1. Field of the Invention
The present invention relates in general to an ink-jet printer, and more particularly to an ink-jet printer including an ink cartridge, a head unit, and a head holder which are carried by a carriage that moves for performing a printing operation, such that the head holder is interposed between the ink cartridge and the head unit.
2. Discussion of Related Art
Conventionally, there is known an ink-jet printer in which an ink cartridge is mounted on a carriage that moves during a printing operation.
The ink-jet printer of the type described above generally includes: a head unit for performing printing or recording by ejecting ink onto a recording medium; a head holder which holds the head unit and which is attached to a carriage that moves in a leftward and rightward direction of the printer, i.e., a direction perpendicular to a feeding direction in which the recording medium is fed; and an ink cartridge removaly mounted on the head holder and accommodating the ink.
The head unit is arranged as follows: the ink is supplied from an ink supply source to an ink inlet of the head unit via an ink supply passage. A plate-type piezoelectric actuator mounted on the head unit selectively applies a predetermined pressure to arbitrary ones of pressure chambers which respectively communicate with a multiplicity of nozzle holes, whereby the ink is ejected from the corresponding nozzle holes. For this end, the head unit includes: a nozzle plate having the nozzle holes through which the ink is ejected for printing; the plate-type piezoelectric actuator which applies the predetermined pressure to the pressure chambers provided in the nozzle plate; and a driver IC which controls a voltage to be applied to the actuator.
On the bottom portion of the ink cartridge where an ink outlet is formed, there is disposed a penetrating member by which the ink cartridge and the head unit are connected to each other. The penetrating member has a flow-passage defining member for defining a flow passage through which the ink is supplied to the head unit, and a joint member functioning as a support via which the ink cartridge is placed on the head holder.
Namely, the ink cartridge is mounted on the upside of the head holder while the head unit is mounted on the downside of the head holder, and the ink cartridge and the head unit communicate with each other through the flow passage defined by the flow-passage defining member so as to penetrate the head holder while the ink cartridge is held by the head holder via the joint member that is disposed on the head holder.
In this respect, an ink-jet printer configured as follows is also known: The ink cartridge is attached to the head holder by pressing the ink cartridge toward the joint member, and a heat sink for cooling the driver IC of the head unit is disposed on the head holder on one side thereof on which the joint member is disposed.
When the printing operation is performed, the ink supplied from the ink cartridge that is mounted on the carriage is fed to the nozzle plate via ink passages formed in the head unit, and the piezoelectric actuator selectively applies the predetermined pressure to the ink, whereby the ink is ejected from the nozzle holes.
The piezoelectric actuator is formed of a piezoelectric ceramic material composed of a ceramic material of lead zirconate titanate (PZT). The piezoelectric actuator includes a plurality of piezoelectric ceramic layers having piezoelectric effect and a plurality of inner electrodes each of which is interposed between adjacent two of the plurality of piezoelectric ceramic layers. Each inner electrode is disposed so as to correspond to a central portion of the corresponding pressure chamber. Portions of the piezoelectric ceramic layers sandwiched by adjacent inner electrodes function as active portions each of which elongates in a stacking direction in which the plurality of piezoelectric ceramic layers are stacked, by applying the voltage to the corresponding inner electrodes.
Upon application of the voltage to the inner electrodes that correspond to arbitrary ones of the plurality of pressure chambers, there is generated, in the active portions, an electric field that is parallel to the polarization direction, whereby the active portions elongate in the stacking direction and the pressure is applied to the ink in the pressure chambers, so that the ink is ejected.
During the printing operation of an image, the temperature of the driver IC which drives the piezoelectric actuator rises. In particular, in a so-called multi-drop type ink-jet printer in which an ink droplet is ejected at a prescribed number for each picture element of the image to be printed and which performs tone production such that each picture element is constituted by the prescribed number of the ink droplet corresponding to image data, the number of times of application of the drive voltage to the head unit in the printing operation of the image significantly increases and therefore the rise in the temperature of the head unit is outstanding.
To deal with the above, there is proposed an ink-jet printing head, as disclosed in JP-A-9-76485 (pages 1-5 and FIG. 3, in particular), for instance, which is equipped with a heat sink for cooling the driver IC of the head unit.
In the ink-jet printer wherein the ink cartridge is removably mounted on the carriage, the head unit needs to be accurately positioned for improving printing accuracy with which the printing by the ink droplet to be ejected onto a sheet of recording paper is performed. Particularly where the carriage carries a plurality of ink cartridges for a color printing operation, there may be caused a risk of color deviation or out of color registration if each head unit is not accurately positioned.
Further, in the carriage which carries the head holder holding both of the ink cartridge and the head unit that has the nozzle plate, the ink cartridge is placed on the head holder such that the ink cartridge is pressed toward the head holder.